Various terms are defined in the following specification. For convenience, a Glossary of terms is provided herein, immediately preceding the claims.
In marine transportation vessels typically used for transporting fluids such as liquefied natural gas (“LNG”), i.e., natural gas that has been liquefied at substantially atmospheric pressure and a temperature of about −162° C. (−260° F.), the fluid containers are integral with the marine transportation vessel's hull. As used herein, the term “Baseline Container Ship” will be used to refer to a marine transportation vessel with fluid containers that are integral with the marine transportation vessel's hull. For transport of LNG and other cryogenic temperature fluids, the fluid containers are often incorporated into a series of insulated holds (known as cold boxes) that extend through the middle two-thirds of a Baseline Container Ship.
U.S. Pat. No. 6,085,528 (the “PLNG Patent”), having corresponding International Publication Number WO 98/59085 and entitled “System for Processing, Storing, and Transporting Liquefied Natural Gas”, and U.S. Pat. No. 6,460,721 (the “Composite Container Application”), having corresponding International Publication Number WO 00/57102 and entitled “Improved Systems and Methods for Producing and Storing Pressurized Liquefied Natural Gas”, both describe containers and transportation vessels for storage and marine transportation of pressurized liquefied natural gas (PLNG) at a pressure in the broad range of about 1035 kPa (150 psia) to about 7590 kPa (1100 psia) and at a temperature in the broad range of about −123° C. (−190° F.) to out −62° C. (−80° F.). Containers described in the PLNG Patent are constructed from ultra-high strength, low alloy steels containing less than 9 wt % nickel. Containers described in the Composite Container Application comprise (i) a load-bearing vessel made from a composite material and (ii) a substantially non-load-bearing liner in contact with the vessel, said liner providing a substantially impermeable barrier to the PLNG. The PLNG Patent and the Composite Container Application are hereby incorporated herein by reference.
Loading and offloading of PLNG into and from a Baseline Container Ship at import and export terminals, respectively, would likely be accomplished with natural gas. It is expected that loading and unloading of PLNG using such a process would be relatively slow and would require that the Baseline Container Ship be berthed at the terminal for a period of days, depending on the PLNG cargo capacity of the Baseline Container Ship.
Barge and lighter carrying ships were designed and built in the 1960's and 1970's for the shipment of cargo to developing ports. Examples of these types of ships include Lighter Aboard SHip (LASH) and SEABEE designs. Both of these types of ships are in the U.S. Merchant Marine reserve fleet. FIG. 1 shows a SEABEE ship 10. The barges 12 on a SEABEE ship 10 are small enough to be lifted using elevator(s) 14 located at the stern of SEABEE ship 10; a SEABEE ship 10 does not take on ballast to float on or float off the barges 12.
A number of companies (Offshore Heavy Transport, Heeremac, etc.) operate heavy-lift ships, primarily for use in the offshore and construction industries. These ships ballast down to float under large objects, then deballast to pick them up and carry them on large, flat decks. The self-propelled heavy-lift vessel then transports its cargo to its destination, where it takes on ballast again to offload or float off the cargo.
In spite of the aforementioned advances in technology, fluid transfer systems and methods that utilize the benefits of ships that ballast down to float cargo on and off, and deballast to pick up and carry cargo, do not currently exist. It would be advantageous to have such systems and methods.
Therefore, an object of this invention is to provide fluid transfer systems and methods that utilize the benefits of ships that ballast down to float cargo on and off, and deballast to pick up and carry cargo. Other objects of this invention will be made apparent by the following description of the invention.